Luc Besson’s Lucy is the ideal film to proceed from the false premise that humans only use ten per cent of their brain, which is to say, a cheerfully and gloriously insane one.

A film in which plotting is accentuated by metaphoric cutaways to National Geographic stock footage. In which a montage of the history of human knowledge ends with a dude solving a Rubik’s Cube. In which unlocked cerebral capacity allows one to use two laptops at once. In which the line “No-one every really dies” is uttered in dead earnest. And that’s just the first hour; by the end, the film goes so far off the rails that it turns into a weird amalgam of The Tree Of Life, 2001: A Space Odyssey and Flight Of The Navigator.

Before all that, we meet Lucy (Scarlett Johansson), an American exchange student in Taipei, mixed up in shady dealings with shady people. Forced to smuggle a new experimental drug in her abdominal cavity, the chemicals end up leaking into her body, allowing her increased access to the furthest reaches of the human mind – and allowing Besson (whose gonzo filmmaking tendencies have been largely absent since 1997’s The Fifth Element) to indulge in increasingly zany flights of stylistic fancy. Morgan Freeman also appears, spouting pseudoscientific nuggets in that delectable intonation that glosses over any research gaps on Besson’s part.

Running just over 80 minutes (please let this be the start of a trend for studio films), Besson finds the perfect pace and shape for a narrative in which the life-or-death stakes of action films are increasingly pushed aside in favour of dopey (but stimulating) philosophical ruminations. It’s also beautifully anchored by Johansson, who handles her transition from blubbering mess to high-functioning autism to dazed superhuman with aplomb – between this and similarly incorporeal recent roles in Her and Under The Skin emerges a fascinating case of actor-as-auteur. “It’s a little rudimentary, but you’re on the right track,” she tells Freeman of his research as her brainpower escalates – also reviewing Lucy in relation to the conveyor-belt-ready Hollywood product it distinguishes itself from.